(1) Field of the Invention
The present invention relates to switching systems and more particularly to a pulse monitor circuit for use in switching systems.
(2) Description of the Prior Art
Current state-of-the-art pulse monitor circuits use retriggerable monostable unit multivibrators. These circuits are designed to operate with the time-out period of the multivibrator set to a time slightly longer than the time between consecutive pulses. Therefore, a missing pulse causes the monostable multivibrator to time-out and an alarm is set. However, retriggerable monostable multivibrators have poor timing tolerances and a low degree of repeatability.
Accordingly it is the object of the present invention to provide a highly reliable low tolerance digital pulse monitor.